The clinical core of the Alzheimer Disease Center will provide for the selection and characterization of patients with progressive dementia and appropriate age-matched controls. Since the neuro-degenerative diseases both appear to be heterogenous syndromes with varying genetic and environmental contributions, we have chosen to examine the characteristics of patients with dementia secondary to both the Alzheimer's disease (AD) and Parkinson's disease (PD). We will develop a registry of 200 patients with clinically diagnosed AD, 100 patients with dementia secondary to PD and compare them to 50 parkinsonian patients without dementia and 50 age- matched controls. Patients and controls, selected by clinical criteria and willingness to consider post-mortem evaluation, will be re-evaluated yearly. The evaluation has been designed to ensure compatibility with the ongoing Alzheimer's disease national data base collection as well as a specialized assessment which would allow further research into comparative studies of etiology and phenominology of AD and PD. We will study the environmental risk factors related to farming and rural living, best examined in the Great Plains region. The registry will select appropriate subjects for studies of epidemiology, neuropsychology, pharmacotherapy, and caregiver services related to AD. Patients will be contacted by phone and mail periodically to ensure that clinical information is complete and current. An autopsy coordinator will provide autopsy information and assist families in post mortem arrangements. Neuropathologic material on well characterized AD patients will be provided to facilitate investigations of cerebral chemistry, histology, and molecular biology. It is our long term goal to develop a coordinated local research program to define the neuropathological correlates of degenerative dementia and interrelationship between brain pathology, cognition and motor function in the elderly.